A gas feed device is operated, including displaying a functional parameter of the gas feed device. A gas feed device may carry out the operation, and a particle beam apparatus may include the gas feed device. A method may include predetermining and/or measuring a current temperature of a precursor reservoir of the gas feed device using a temperature measuring unit, where the precursor reservoir contains a precursor to be fed onto an object, loading a flow rate of the precursor through an outlet of the precursor reservoir from a database into a control unit, said flow rate being associated with the current temperature of the precursor reservoir, and (i) displaying the flow rate on the display unit and/or (ii) determining the functional parameter of the precursor reservoir depending on the flow rate using the control unit and informing a user of the gas feed device about the determined functional parameter.